Apparatus for removal of lithography from metal surfaces

ABSTRACT

The applied finish or lithography of articles, such as flat metal plates or cylindrical containers is removed by passing the article through a zone of intense heat and then immediately into a second zone where the surface of the article is brushed while hot and while the lithography is soft. A plurality of articles are urged seriatim along a linear path through an induction heating coil and are then engaged by one or more wire brushes which also rotate a container during the brushing operation. The process may be carried out rapidly and automatically without damage to the soldered seam or metallurgy of a container.

United States Patent 1 1 Gregory et a1.

[ Dec. 30, 1975 Ave., Westchester, 111. 60153; Jack R. Randolph, Phoenix, Ariz. 85000 22 Filed: Jan. 16,1974

21 Appl. No.: 433,681

Related US. Application Data [63] Continuation-impart of Ser. No. 302,495, Oct. 31,

1972, Pat. NO. 3,801,369.

[56] References Cited UNITED STATES PATENTS 4/1915 Eberhart 134/19 UX 3/1930 Lakeman 134/19 X 8/1942 Bailey 134/19 UX 7/1953 Leece 15/88 X Primary ExaminerEdward L- Roberts Attorney, Agent, or FirmGary, Juettner, Pigott & Cullinan [57] ABSTRACT The applied finish or lithography of articles, such as flat metal plates or cylindrical containers is removed by passing the article through. a zone of intense heat and then immediately into a second zone where the surface of the article is brushed while hot and while the lithography is soft. A plurality of articles are urged seriatim along a linear path through an induction heating coil and are then engaged by one or more wire brushes which also rotate a. container during the brushing operation. The process may be carried out rapidly and automatically without damage to the soldered seam or metallurgy of a container.

7 Claims, 8 Drawing Figures US. Patent Dec. 30, 1975 Sheet 10f3 3,928,883

ll lul.

US. Patent Dec. 30, 1975 Sheet 2 of3 3,928,883

@wmw Mg? i U..S. Patent Dec. 30, 1975 sheeg 3 of3 3,928,883

1 APPARATUS FOR REMOVAL OF LITHOGRAPHY FROM METAL SURFACES CROSS REFERENCE This is a continuation-in-part of my copending application, Ser. No. 302,495, filed Oct. 31, 1972 now US. Pat. No. 3,801,369.

BACKGROUND OF THE INVENTION Aerosol containers have gained wide acceptance for the storing and dispensing of a wide variety of products. Such containers are made of steel sheet to withstand considerable pressure and are usually cylindrical in shape, having a soldered axial seam along one side, and soldered seams joining the cylindrical wall to the top and bottom. The walls are plated or coated with tin to prevent rusting of the steel. The product under pressure within the container is dispensed by a valve arrangement usually located at the top of the container.

Aerosol and similar containers are normally provided with lithography in the form of a coating of paint, enamel, varnish or other suitable finish, which protects the metal surface from deterioration and contains printed information to identify the product. In most cases, lithography comprising the product name, description, instructions for use and other information or design is printed on the container surface in accordance with specifications provided by a particular customer, and the lithography is then covered by a clear varnish.

After the lithography has been applied, the container acquires a specific identity that is useful only to the customer for whom it was made, even though the container alone might be useful in other applications. Large scale production and misapplication of lithography often results in an excessive number of a given lot of containers that cannot be sold. Due to the high cost of containers of this type, it would be desirable to devise a method for completely removing the lithography to allow use of the container for another purpose.

In order to change the identity of the container, it is possible to apply a printed label or paper cover over the cylindrical surface, which hides the old lithography and allows use of the container for a different product. This procedure may be dangerous, however, because the label or cover is normally applied with minimal amounts of adhesive and is susceptible to removal. For example, if a container with hair spray or deodorant lithography was converted by application of a label to a paint spray container, and the label was later inadvertently removed, the container would become a dangerous instrument, viz, an unsuspecting customer would use paint as hair spray or deodorant.

The use of solvents for the removal of lithography is not feasible because the varnishes used to overcoat the printing resins are of the silicone or epon type and resist most standard solvents. There are other drawbacks in the use of solvents, such as possible contamination of the interior of the container, disposal of waste solvent and lithography residue, health and safety hazards in the use of volatile solvents, and high solvent costs.

SUMMARY OF THE INVENTION The present invention provides an apparatus for completely and inexpensively removing surface lithography from a metal article, whereby the article may be used in another application without the possibility of confusion. The lithography is removed by first softening the lithography by rapid and uniform heating of the surface, followed by brushing of the surface. The arti cles, especially containers may then be used for any desired purpose by applying an appropriate label. The process allows for complete removal of the lithography without damage to the soldered seams or to the tin plating of a container.

The apparatus generally comprises a means for carrying or conveying the articles through a heating zone, preferably through the coils of an induction heater, and means for passing each article between a rotating brush and a bearing support, whereby the containers are brushed while being rotated.

THE DRAWINGS FIG. 1 is a simplified elevational view of the apparatus of the present invention, illustrating the various process steps of the invention;

FIG. 2 is a sectional view taken substantially along section line 22 of FIG. 1;

FIG. 2a is a sectional view taken substantially along section line 2a2a of FIG. 1;

FIG. 3 is a simplified elevational view of another embodiment of the present invention;

FIG. 4 is a sectional view through the apparatus of FIG. 3 taken along section line 44 thereof;

FIG. 5 is a simplified perspective view of a further embodiment of the present invention;

FIG. 6 is a sectional view taken along section line 66 of FIG. 5; and

FIG. 7 is a simplified elevational view of another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiment of the invention is shown in FIGS. 1 and 2, which illustrate an apparatus for removing lithography from the cylindrical surface 10 of an aerosol container 12 having the usual top dome 14 and valved outlet 16. It will be appreciated, however, that the apparatus shown is capable of removing cured or hardened paint, enamel, varnish, and any other similar coating from a cylindrical object of any length. Moreover, as will be hereinafter described, the apparatus of the present invention is also capable of removing hardened paint, varnish or similar finishes from flat metal sheet.

The device generally comprises conveyor means for moving articles along a line, heating means for heating the surface of the article to soften the lithography thereon, and abrasion means. engageable with the heated surface of the article to remove the softened lithography therefrom.

In the preferred embodiment, the conveyor means, generally indicated at 18, preferably comprises a pair of spaced parallel shafts 20 and 22, one of which is driven, with each shaft, respectively, having a pair of axially spaced pulleys 24 and 26 secured thereon. Respective pulleys 24 are aligned with the other pulleys 26 to mount a pair of spaced parallel belt loops 28 and 30, which are stretched between their respective pulleys to define a substantially horizontal upper moving bed upon which the containers may be conveyed in a straight line on their cylindrical surface in a direction indicated by arrows in FIG. 1.. The belts 28 and 30, which are composed of non-conductive reinforced rubber or the like, are spaced apart a distance which is 3 less than the diameter of the container 12, such that the container is nested between the upper flights of the belts 28 and 30, as shown in FIG. 2.

The heating means is preferably in the form of a spiral induction coil 32 having a sufficiently large enough diameter to closely accommodate free passage of the belts 28 and 30 and the conveyed container 12 therethrough. The induction coil is conventional and comprises hollow copper tubing through which cool water is circulated, with the tubing being connected to a source of high frequency direct or alternating current. As the container passes through the coil on the belts, it is heated by means of eddy currents induced by the high frequency field surrounding the coil. The coil is of sufficient length and size to cause rapid and uniform heating of the entire container in a very short period of time, since the time residence of the container within the induction coil must be a fraction of a second to allow fast and efficient treatment of a large number of containers. In the embodiment shown in FIG. 1, the coil 32 is preferably energized continuously while the containers are successively moved therethrough.

The temperature to which the container is heated is important and must be controlled by the length of the induction coil, the number of turns in the coil, the spacing between adjacent coil turns, as well as the speed of the conveyor. Generally, the maximum temperature reached by the container must be high enough to soften the surface coating but must be less than the melting point of the solder in the side joint commonly found in containers of this nature. Too high a temperature will cause leaks or structural failure in the container and may burn the container or melt the tin coating on the steel. Generally speaking, these conditions are attained if the containers are heated to a temperature of from about 340 to 390F, although temperatures of up to 450F are possible with some types of containers.

The means for abrading the containers comprises a separate conveyor means cooperating with the first conveyor and one or more driven cylindrical brushes engageable with the cylindrical surface of the container.

As shown in FIGS. 1 and 2a, a sprocket 34 having a radius less than the pulleys 26 is rotatably mounted between said spaced pulleys on the exit end of the conveyor 18, and a driven second sprocket 36 is mounted on a shaft 38 spaced from and parallel to the shaft 24. The roller chain 40 having outwardly projecting spaced dogs or lugs 42 is wrapped around the sprockets and is driven thereby. In addition, a pair of spaced parallel fixed rods 44 extend substantially in the same plane as the upper flight of the conveyor 18 from the exit end thereof with the chain 40 located therebetween. The rods 44 are spaced apart for a distance less than the diameter of the containers 12 so as to support the containers during the brushing operation.

As the containers exit from the belt conveyor 18, they are transferred to the rods 44 and are then engaged by a lug 42 of the chain 40, said lug being of sufficient length to extend above the level of the rods and engage a shoulder of the can between the dome l4 and the cylindrical surface 10. The lugs 42 serve to push the container along the rods 44 and into engagement with successive ones of a plurality of rotating brushes 46, which may be mounted on a common shaft 48.

The brushes 46 are preferably wire brushes, comprising a plurality of spaced disks to provide a series that is longer than the length of the container. Narrower brushes are preferred because they tend to conform better to the actual shape of the container and better accommodate dents which may be present in the surface of the container. Although high quality wire brushes having 0.006 inch diameter bristles are preferred, one sizes and materials, such as nylon, may be successfully employed. The shaft 48 is preferably adjustably spaced a sufficient distance directly above the chain such that a moving container will be engaged between the rods 44 and successive brushes 46. The axis of the shaft 48 is in the vertical plane of the container axes to hold the containers on the rods 44 without slippage to either side. As the containers are moved into engagement with the brushes 46, the rotary motion of the brushes causes the containers to be rotated somewhat about their axes, thereby exposing the entire cylindrical surface of the container to brushing.

Although the containers may be conveyed through the apparatus in a contiguous relationship, it has been found preferable to convey the containers through the coil 32 in a slightly spaced relationship, i.e., at least about a 1 inch spacing, which increases the efficiency and uniformity of the heating process. When conveyed in a contiguous relationship, it has been found that the ends of the container are not sufficiently heated by the induction coil, and traces of lithography are not removed at the ends.

Means, as shown in the left hand portion of FIG. 1, are provided for placing containers onto the belt conveyor in a timed, spaced relationship. A pusher, comprising a power cylinder 50 is mounted on a support 52 and includes an extendable and retractable rod 54 having an enlarged head 56 engageable with the crown 14 or valve 16 of a container 12. A pair of spaced parallel rods 58 are mounted on the support 52 with the rod 54 and head,56 operating in parallel therebetween, said rods extending parallel to and in register with the top flight of the conveyor 18. The rods 58 serve to support successive containers which are pushed off the rods and onto the conveyor 18 in a predetermined sequence.

The cylinder 50 is preferably activated at regular intervals by a suitable valve (not shown) to push successive containers 12 onto the conveyor 18. A loading mechanism 60 comprises an inclined ramp or a sequence feed mechanism is connected to the support 52 in front of the rod head 56 and serves to load successive of a plurality of containers 12a onto the spaced rods 58.

In operation, it may be seen that each container travels in substantially a straight line from the pusher to the heater and then to the brusher, and the containers travel in a spaced relationship with their domes 14 facing away from the direction of travel to assure proper engagement with the lugs 42. The coil 32 is continuously energized, and as each container is passed through the coil, it is quickly heated, whereby the lithography on the cylindrical surface becomes soft. The heated container is then passed into the brushes 46, which physically removes the lithography as the container is being pushed and rotated on the rods 44. The containers may then be led away from the apparatus and may also be inverted and cleaned free of dust by a jet of pressurized air. Thereafter, the containers are rendered suitable for use by the application of a label on the cylindrical surface.

The version of the invention shown in FIGS. 3 and 4 allows the containers 60 to be cleaned in a contiguous fashion. A pair of spaced support members 62 and 64 extend through an induction coil 66 and beneath a brush assembly 68. A power cylinder 70 equipped with a rod 72 having a pusher 74 is engageable with the bottom surface of successive containers introduced on their sides onto the supports 62 by a suitable hopper or the like. The containers 60 are pushed axially in a contiguous fashion through the coil 66 to be heated and then through the brush assembly 68, which serves to rotate and brush the hot containers free of lithography.

The coil 66 is arranged in a particular manner to assure that the contiguous containers are uniformly heated. For this purpose, the containers 50 are jogged on the supports 62 by the cylinder 70 into successive forward positions. The coil 66 has more closely spaced and additional turns in the zones corresponding to the ends of the containers than in the middle, such that additional heat is generated at the ends. The coil is long enough to accommodate at least two and preferably at least three containers at any given time, such that the containers are progressively heated by successive portions of the coils as they are indexed forward at fixed intervals and distances, with one container pushing the next successive container through the apparatus.

In the version shown in FIGS. 3 and 4, the coil is not energized continuously but is pulsed in sequence with the container movement, or each time a container is advanced into a new position. In this manner, the containers gradually reach the desired temperature for lithography removal and are heated evenly, notwithstanding their contiguous relationship.

The embodiment shown in FIGS. 5 and 6 illustrate a different form of heating. The containers 80 are slidably conveyed on chain drive 86 including spaced lugs 88 projecting from the chain and engaging and pushing the ends of the conveyors.

The initial portion of the rods 82 and 84 and chain drive 86 are surrounded or at least partially enclosed by an oven wall 90 having a plurality of electrical resistance heating elements 92 mounted therein, said elements being spaced from but substantially parallel to the rods 82 and 84. The energization of the elements 92 serves to heat the interior of the chamber, thereby heating the containers as they pass therethrough.

As in the previous embodiments, the far end of the conveying line is equipped with suitable brushes 94 which are driven by a motor 96. In the embodiment shown, the rods 82 and 84 are rotatable about their axes. As the brushes 94 engage the containers 80, the rods 82 and 84 are rotated, thereby rotating the supported containers in the heating chamber to provide more uniform heating.

Although the present invention has been described in connection with cylindrical objects and is particularly adapted thereto, it will be understood that the principles of the invention may also be applied to remove the organic finish from other metal objects. As an example, an apparatus for removing the lithography or paint finish from metal plates is shown in FIG. 7.

In the apparatus of FIG. 7, individual flat metal plates having an organic surface finish are conveyed along a line by a suitable conveyor 102, which may comprise two or more parallel non-conductive belts 104 driven around spaced pulleys 106 and 108. An induction coil 110 encircles a portion of the top flight of the conveyor and is shaped to provide a radiating surface that is generally parallel with the finished surface and closely spaced therefrom. The coil 110 is connected to a suitable electrical source as previously described, and serves to heat the metal adjacent the finished surface to a temperature which softens the finish. Other types of heaters may be employed as previously described.

After the finish has been softened, the finish is removed by means of one or more rotating wire brushes 112 which engage the finished surface as the article is supported on the conveyor. In the case of flat surfaces, it is preferable to rotate the brushes around an axis perpendicular to the travel of the conveyor.

We claim:

1. Apparatus for removing lithography from the cylindrical outer surface of a container comprising conveyor means for moving said container axially along its outer surface, means for heating the container substantially uniformly while being thus moved to a temperature sufficient to soften the lithography without disturbing the structure of the container, brush means for brushing the cylindrical surface of the container while it is being moved, and means to allow rotation of said container while being brushed by said brush means.

2. Apparatus for removing lithography from the cylindrical outer surface of a container, comprising conveyor means for moving said container axially on its outer surface, pusher means at the entrance end of said conveyor means for pushing successive containers onto said conveyor means, means for heating the container substantially uniformly while being thus moved to a temperature sufficient to soften the lithography, and brush means for brushing the cylindrical surface of the heated container.

3. The apparatus of claim 2 including means for rotating the container while being operated thereon by said brush means.

4. The apparatus of claim 1 wherein pusher means are provided at the entrance end of said conveyor means for pushing successive containers onto said conveyor means.

5. The apparatus of claim 1 wherein said conveyor means comprises a pair of spaced belts moving in the same direction, and said means for heating comprises an induction coil surrounding said belts and having an internal diameter large enough to allow passage of said container therethrough on said belts.

6. The apparatus of claim 1 wherein said brush means comprises a plurality of spaced brushes rotating on an axis parallel to the axis of said container.

7. The apparatus of claim 6 wherein a pair of spaced rods support said container beneath said brushes. 

1. Apparatus for removing lithography from the cylindrical outer surface of a container comprising conveyor means for moving said container axially along its outer surface, means for heating the container substantially uniformly while being thus moved to a temperature sufficient to soften the lithography without disturbing the structure of the container, brush means for brushing the cylindrical surface of the container while it is being moved, and means to allow rotation of said container while being brushed by said brush means.
 2. Apparatus for removing lithography from the cylindrical outer surface of a container, comprising conveyor means for moving said container axially on its outer surface, pusher means at the entrance end of said conveyor means for pushing successive containers onto said conveyor means, means for heating the container substantially uniformly while being thus moved to a temperature sufficient to soften the lithography, and brush means For brushing the cylindrical surface of the heated container.
 3. The apparatus of claim 2 including means for rotating the container while being operated thereon by said brush means.
 4. The apparatus of claim 1 wherein pusher means are provided at the entrance end of said conveyor means for pushing successive containers onto said conveyor means.
 5. The apparatus of claim 1 wherein said conveyor means comprises a pair of spaced belts moving in the same direction, and said means for heating comprises an induction coil surrounding said belts and having an internal diameter large enough to allow passage of said container therethrough on said belts.
 6. The apparatus of claim 1 wherein said brush means comprises a plurality of spaced brushes rotating on an axis parallel to the axis of said container.
 7. The apparatus of claim 6 wherein a pair of spaced rods support said container beneath said brushes. 